I figured that he was on his way out of there, to take advantage of the market created for him and his career by the positive performance of his team and the negative issues at some premier programs around.

COMPLETE SPECULATION
I speculate that the back channel conversations have gone on with him and that is why he is holding tight.

I see the following NFL teams needing a coach (and I don't do this speculation a lot or well)
Atlanta
NY Giants
NY Jets
SF
Carolina
Miami (this is where I think Harbaugh lands)